This invention relates to fastening. In particular, it is directed to a fastening clip and an apparatus for use with that clip, the clip being used to fasten together crossing elongate members and has a specific, but not limiting, use to secure the lattice type structure of reinforcing rods of the type used in the construction of steel rod reinforced concrete slabs.
Concrete slabs as used in the foundation for a building or as a suspended ceiling or floor incorporate an open lattice or grid of steel rods for strength. To prevent these rods from sagging under the weight of the wet concrete until it has set, the rods are tied together. It is usual to secure each rod to each other rod that crosses it along its length. The usual securing method is, at each such intersection, to wrap a short length of wire around both rods and then tightly twist the ends to secure the rods in place. These wire tying operations are usually undertaken manually using some form of gripping device to twist the wire.
Even in relatively small constructions, the time taken to fabricate the reinforced steel lattice is significant adding noticeably to the overall cost of the building construction. Further disadvantages include (1) operator fatigue due to the large number of ties to be performed, thus effectively reducing the rate of tying and actually adding to the time and therefore cost of completing the construction; (2) muscular and related problems for the operator as the operator must bend over and/or squat in order to effect the tie; (3) tying is not uniform being dependent upon the efficiency of the operator, thus potentially leading to the aforementioned sagging of the rods before the concrete sets. Also, after the tie is made, the excess wire length is cut resulting in small lengths of wire which tend to settle to the base of the wet concrete slab. When this slab is a suspended floor, these wire remnants are visible on an exposed surface where they oxidise leading to unsightly rust stains. More time is thus consumed in removing these small fragments of wire.
One prior attempt to alleviate such disadvantages is to secure the rods together by welding. However, welding of such load bearing structures is banned in some countries as it may alter the temper and thus strength of the metal in and adjacent to the weld zones. Other disadvantages include (1) operators are exposed to the noxious welding gases and must have frequent periodic medical checks; (2) there is a wastage of material if a mistake is made as a weld cannot be reversed; (3) the welding flame, because of the potential damage that it can inflict to an unshielded eye, must be screened from passers-by; and (4) it still fails to alleviate the muscle fatigue of the operator.
Another prior art attempt to overcome these disadvantages is disclosed in U.S. Pat. No. 3,169,559 wherein a tool is described which automatically twists the ends of a substantially U-shaped clip placed on the two crossing members. However, this tool is only of limited use as the tool head must pass through the gaps of the lattice work to function thus preventing its use on close-knit lattice work. Further, the clips are placed diagonally on the cross members leading to poor stability because of the reduced contact between the clip and rod. Another disadvantage is that the tool twists but does not sever the dip ends thus requiring a second separate cutting action to complete the fastening process.
Yet another prior art attempt to resolve at least some of these disadvantages is described in U.S. Pat. No. 4,653,548 and its Australian equivalent 574043 whereby the ends of two arms of a wire clip can be twisted and the ends severed as the final phase of the fastening. However, this solution still requires two distinct manual operations, the first is the positioning of the clip where required and the second is the actual engagement of the clip with the tool. The cut ends are also still not contained and therefore have to be removed in a third operation if necessary.
It should also be noted that all of these prior art attempts are only applicable to the use of a wire which can only provide limited strength capabilities.
It is thus a general object of the present invention to overcome, or at least ameliorate, one or more of the above-mentioned disadvantages.
According to a first aspect of the present invention, there is provided a clip for use in the fastening together of two crossing substantially elongate upper and lower members, said dip including a body with a recess extending from a first face to near a second face substantially opposite said first face to form a first arm and a second arm, said recess terminating with a shaped portion of a configuration substantially complementary to the exterior surface of said upper member wherein, when said clip is in a fastened position, said recess can engage said upper member and said first arm and said second arm can engage said lower member sufficient to fasten said upper member and said lower member together.
Preferably, said body is substantially polygonal in elevation.
Preferably, said polygonal elevation is rectangular.
Preferably, said shaped portion is substantially arcuate in elevation.
Preferably, said recess converges from said first face to near said second face.
According to a second aspect of the present invention, there is provided an apparatus to install a clip as hereinbefore described, said apparatus including
a base plate which has an aperture through which an intersection of a said upper member with a said lower member can be viewed;
retaining means to retain at least one of said clip;
positioning means to enable a said clip to be released from said retaining means and pass through said aperture to be positioned on said upper member at said intersection; and
securing means to secure said first arm and said second arm to said lower member when a said clip has been positioned at said intersection.
Preferably, said base includes a locating means to assist in locating said apparatus at a required said intersection.
More preferably, said retaining means retains a plurality of said clip.
Preferably, said positioning means includes a shearing means adapted to shear sequentially a series of said clip from said retaining means.
Preferably, said securing means includes a first lever which can engage and bend said first arm to engage said lower member and a second lever which can engage and bend said second arm to engage said lower member, engagement of said first and second arm with said lower member being sufficient to fasten together said lower member and said upper member.
Preferably, said apparatus includes a handle from which said positioning means and said securing means can be operated.
In a first embodiment of the apparatus of the present invention, positioning of said clip and subsequent engagement of said first arm and said second arm with said lower member is undertaken mechanically.
In a second embodiment of the apparatus of the present invention, positioning of said clip and subsequent engagement of said first arm and said second arm with said lower member is undertaken hydraulically.
In a third embodiment of the apparatus of the present invention, the operation of the apparatus can be undertaken electrically, electronically or by gas power.
As a third aspect of the present invention, there is provided a method of fastening together two crossing substantially elongate upper and lower members wherein a clip as hereinbefore described is secured at an intersection of said lower and upper member using an apparatus as hereinbefore described.
A fourth aspect of the present invention is the provision of a lattice-type arrangement comprising a series of crossing lower and upper members wherein each intersection of said upper and lower member has been fastened with a clip as hereinbefore described.